1. Field of the Invention
The invention relates to an adjustable supporting device, and especially relates to an adjustable supporting device capable of being folded.
2. Description of the Prior Art
Many devices are fixed or placed on other objects by use of supporting devices. For example, a monitor is fixed on a supporting device and then is placed on a table. For use convenience of a user, the supporting device is designed to be adjustable in height and angle. In practice, also for storage convenience, the supporting device usually consists of a plurality of pivotally-connected supports. In use, the user can expand the supports till a required height and angle therefor is obtained, so that the monitor thereon can fill the user's requirement. In storage, for storage convenience, the user can shrink or fold the supports to reduce required space for storage as small as possible. For convenient adjustment to the expanded status of the supports for the user, there is usually no limitation on relative rotation of any adjacent two of the supports. However, when the user adjusts the expanded status of the supports (mainly to rotate the supports), it is very probable to incautiously clamp fingers of the user by the supports due to an unexpected folding induced by an improper rotation operation. Furthermore, when the user needs to perform the adjustment operation by a single hand for some reason, an improper rotation occurs more easily. For this issue, an adjustable supporting device having a positioning function by use of a washer set at its pivotal connection is available, but the washer set performs the positioning function only by use of interference structure and compact assembly to increase friction force for resisting an improper rotation by the user, which cannot avoid the improper rotation exactly. Therefore, the abovementioned adjustable supporting device cannot avoid the unexpected folding effectively, so it is unavoidable that damage due to an unexpected folding induced by an improper rotation operation.